Electrospinning is an efficient process that produces nanometer-to-micrometer sized fibers with tunable diameter (Li et al. Nano Letters 3, 1167 (2003); Darrell & Iksoo Nanotechnology 7, 216 (1996); Fong et al. Polymer 40, 4585 (July, 1999); incorporated by reference in their entireties). Nanofiber films produced by electrospinning provide a promising platform for biomaterials. Electrospinning has been traditionally used to form fibers from high molecular weight polymers, but has recently been extended to supramolecular assemblies, such as surfactants (Cashion et al. Langmuir 26, 678 (2010); McKee et al. Science 311, 353 (2006); herein incorporated by reference in their entireties), peptides (Singh et al. Adv Mater 20, 2332 (2008); herein incorporated by reference in its entirety), host-guest molecules (Yan et al. Chem Commun 47, 7086 (2011); herein incorporated by reference in its entirety), and cyclodextrin (Celebioglu & Uyar. Langmuir 27, 6218 (2011); herein incorporated by reference in its entirety). However, electrospinning small molecules requires high concentrations and organic solvents. Organic solvents can be undesirable in biomedical material processing because residual solvent needs to be removed; additionally, non-aqueous conditions can cause denaturation of bioactive proteins, preventing bioactivity.
Peptide amphiphiles (Hartgerink et al. P Natl Acad Sci USA 99, 5133 (2002); Hartgerink et al. Science 294, 1684 (2001); herein incorporated by reference in their entireties) (PAs) are a class of self-assembling molecules that are composed of a hydrophobic segment conjugated to a sequence of amino acids. PAs can form long, high aspect ratio filaments in water and have been studied for a range of applications in regenerative medicine (Mata et al., Biomaterials 31, 6004 (2010); Shah et al., P Natl Acad Sci USA 107, 3293 (2010); Huang et al. Biomaterials 31, 9202 (2010); Webber et al., P Natl Acad Sci USA 108, 13438 (2011); herein incorporated by reference in their entireties). PA bioactivity is derived from presentation of biological epitopes on the surface of self-assembled nanostructures that form in solution. The rheological properties of these materials can be tuned by concentration and peptide sequence (Pashuck et al. Journal of the American Chemical Society 132, 6041 (2010); herein incorporated by reference in its entirety).